As a transmitter/receiver system, a system having one or more mobile telephones, which may include one or more vehicle telephones, and a transmitter/receiver management apparatus that manages transmission and reception between the mobile telephones has been proposed. Transmission and reception is carried out using a carrier in an ultra-high-frequency band, e.g. an 800-MHz band at the lowest, a 1.5-GHz band, 1.9-GHz band, a 2-GHz band, etc.
In such a transmitter/receiver system, as the frequency band of the carrier becomes higher, the rectilinear propagation characteristic of the carrier becomes stronger. That is to say, reflection of the electromagnetic waves reduces, so that communications become difficult in buildings, especially deep inside buildings. The antenna also suffers from shadowing by the human body, so that, when the mobile transmitter/receiver is put into a pocket, the reception performance of the antenna may deteriorate remarkably in comparison with a hand-held state.
On account of the effect electromagnetic radiation produced by mobile telephones has upon medical appliances, it is either requested that mobile telephones be powered off in hospitals or, in some cases, devices for intentionally generating interference (i.e. jamming devices) are provided to disable telephone calls. Furthermore, it is requested that mobile telephones be powered off as a courtesy in restaurants, hotels, trains, etc. In these cases, mobile telephones cannot receive calls, and are therefore useless in enabling the person carrying the mobile telephone to respond to an emergency.
In the early period of the marketing of PHS telephones (PHS=personal handyphone system; a system in which the phone functions as a cordless phone in a limited-range, home environment and as a mobile phone elsewhere), a mobile/portable telephone combining the functions of a PHS and a pager was proposed that took into consideration the fact that the establishment of an infrastructure for PHS telephones would take time. According to the proposal, if such a PHS telephone was outside its area of communication, the pager would be used for paging. However, this type of mobile/portable telephone necessitates contracts with both PHS and pager service providers. Furthermore, the pager of such a mobile/portable telephone needs to be used when communication is not possible by calling its PHS number. Thus, a caller is require to appropriately choose between the PHS number and the pager number of the mobile/portable telephone being called/paged.